High blood pressure is often linked to heart disease and cognitive decline. A new study suggests that fluctuations in blood pressure can be a warning sign of dementia.

Short-term fluctuations of blood pressure within a day, as well as over several days or weeks, are associated with impaired cognition, according to researchers from the University of South Australia, who conducted the latest study.

Higher variations in systolic pressure – the blood pressure value that measures the pressure in arteries when a heart beats – were found to be linked to arterial stiffening associated with heart disease.

Blood pressure normally fluctuates with stress, exertion, medication and diet. When there are strong fluctuations in blood pressure, the condition is known as labile hypertension.

"Clinical treatments focus on hypertension while ignoring the variability of blood pressure. Blood pressure can fluctuate across different time frames – short and long – and this appears to heighten the risk of dementia and blood vessel health," lead author Daria Gutteridge, from Cognitive Ageing and Impairment Neuroscience Laboratory (CAIN) in the University of South Australia, said in a news release.

Dementia is a general term used to denote memory loss and cognitive decline, or the loss of language, problem-solving and other thinking abilities.

The findings were based on blood pressure monitoring and cognitive evaluation of a group of 70 healthy older adults. The participants were aged from 60 to 80 years and had no signs of dementia or cognitive impairment.

The blood pressure variability of the participants within a day was tested using a 24-hour ambulatory BP monitor. The day-to-day fluctuations were monitored using a home-based BP monitor for four days, in the mornings and evenings. Researchers conducted transcranial Doppler sonography and pulse wave analysis to test arterial stiffness in the brain and arteries.

"We found that higher blood pressure variability within a day, as well as across days, was linked with reduced cognitive performance. We also found that higher blood pressure variations within the systolic BP were linked with higher blood vessel stiffness in the arteries," the researchers said.

The team believes the findings will help recognize blood pressure variability as an early clinical marker or a treatment target for cognitive impairment.

"These results indicate that the different types of BP variability likely reflect different underlying biological mechanisms, and that systolic and diastolic blood pressure variation are both important for cognitive functioning in older adults," the researchers said.